1. Field of the Invention
This invention relates to a non-contact eye pressure meter for blowing, for example, air against the cornea of an eye to be examined to thereby deform the cornea and detecting the deformation thereof, for example, photoelectrically.
2. Related Background Art
The prior-art eye pressure meter of this type is known from U.S. Pat. No. 3,585,849 and U.S. Pat. No. 3,756,073 wherein as shown in FIG. 1A of the accompanying drawings, the air from an air cylinder mechanism 1 is blown as an air stream against the cornea Ec of an eye E to be examined through a nozzle 2a in an objective lens 2. It is usually the case that such meter is provided with a cornea deformation detecting system for projecting a light onto the cornea Ec from an oblique direction and receiving the cornea-reflected light in an oblique direction. That is, the light from a light source 3 such as a light-emitting diode is projected onto the cornea Ec of the eye E to be examined form an oblique direction through a projection optical system 4, and the reflected light therefrom is received by a photoelectric light-receiving element 6 from an oblique direction through a light-receiving optical system 5. Reference numeral 7 designates a finder optical system.
The prior-art eye pressure meter has a disadvantage that its structure is unavoidably complicated bacause both the projection optical system 4 and the light-receiving optical system 5 are disposed in oblique directions relative to the cornea Ec.
Also, U.S. Pat. No. 3,832,890 discloses, as shown in FIG. 1B of the accompanying drawings, the provision of a cornea deformation detecting system for projecting a light onto the cornea Ec from the direction of the optic axis and receiving the cornea-reflected light in the direction of the optic axis. That is, the light emitted from a light source 3a irradiates the cornea Ec so as to travel toward the focus of the cornea Ec through a lens 7a and an objective lens 2, and the light reflected by the cornea Ec is received by a photoelectric light-receiving element 6a through the lens 7a and the objective lens 2.
However, in U.S. Pat. No. 3,832,890, the light source 3a and the photoelectric light-receiving element 6a are in conjugate relationship with respect to the optical system whose reflecting surface is provided by the cornea before deformed and therefore, the deformation of the cornea cannot be recognized with good accuracy.
Moreover, the applied light beam passing through the interior of the nozzle 2a and the applied light beam passing through the exterior of the nozzle 2a differ in situation from each other and therefore, it is possible that random light is picked up when the deformation of the cornea is detected.